When a patient has an arrhythmia (an irregular heartbeat), cardiologists will often treat the disorder by inserting two tube-like catheters into the patient’s heart. The first catheter is used for mapping out the heart tissue, identifying the location of cells that are causing the arrhythmia. The second catheter, which has an electrode on the end, is then directed to those locations, where it kills the aberrant cells in a process known as ablation. Scientists have recently developed a single catheter with added stretchable electronics, however, that does both jobs in one step.